Messages from the Cinereous and Streaked Bulbuls

In the winter of 2014/2015, Singapore experienced a flood of Cinereous Bulbuls and Streaked Bulbuls. An influx of some sort, it seemed. These typically uncommon bulbuls appeared all over the country, with observations including a flock of nearly 200 Cinereous Bulbuls at Pulau Ubin. During that period, many other surprises showed up: two separate Green Broadbills, Yellow-eared Spiderhunter, Yellow-vented Flowerpecker, and Thick-billed Flowerpecker to name a few. Most of them were species that are rare visitors to Singapore (the Green Broadbill especially, being the first two records since their extirpation in 1941) though common in the lowlands of the region, such as the forest patches of Johor just an hour’s drive by car, or the islands in Riau a boat ride away.

The next few seasons were lacklustre with regards to these groups of birds despite the rapid spike of birdwatchers in the country. Both bulbuls only appeared sporadically and in much smaller numbers, and regional lowland rarities (?) continued to be found but at a rather slow pace. In the 2018/2019 season, a handful of Cinereous Bulbuls appeared and were once again accompanied by some Streaked Bulbuls. Their numbers dwindled through summer, and the 2019/2020 season was a similar case.

Then in the winter of 2021/2022, Singapore observed a familiar scene of mass Cinereous Bulbul arrivals. Streaked Bulbuls followed suit, and multiple rare regional species showed up in Singapore as if their calendars were synchronised: two Black-thighed Falconets (the first since 1990), Green Broadbill (first since 2014), Scarlet Minivet (first since 2001), Yellow-vented Flowerpecker, and Scarlet-breasted Flowerpecker (first confirmed record for Singapore).

The peaks and troughs of Cinereous Bulbul (blue), Streaked Bulbul (red), and locally significant Sundaic visitors (green) sightings in Singapore. Sundaic visitors are considered “locally significant” for the purposes of this illustration if they have less than 10 records in the last 10 years. The table below this article lists all the records of these locally significant Sundaic species from this illustration. Note that a single record is defined as an individual or group of individuals present at one site for a period of time. So although there were hundreds of Cinereous Bulbuls across Singapore in both the 2014 and 2021 peaks, the number of records is far smaller.

These sightings are more than just déjà vu; they possibly hint towards some form of ecological force driving the birds southwards that we are yet to understand (assuming they primarily came from Johor). Indeed, unorthodox movements of birds – be it at a large or small scale – are periodically observed. In 2019/2020 we had a spate of Indochinese birds arriving in Singapore, and just last season we were kept busy with species that typically winter in the Indian and Middle-eastern region (remember the Cinereous Vulture, Amur Falcon, Black Redstart and Spotted Flycatcher?).

Very recently in May we also observed a rush of regional species to Pulau Ubin, with Black-and-red Broadbill, Black-and-white Bulbul, Lesser Green Leafbird and Scarlet-breasted Flowerpecker showing up. Strangely, Cinereous and Streaked Bulbuls were absent from the rave, and the birds were concentrated to Chek Jawa but not elsewhere in Singapore – perhaps the cause for the latest event differs from the seemingly periodic influxes we get. Could it have been due to land-use change in the region? Was there a particular tree in Chek Jawa blocked from our views that provided a very attractive food source? We don’t know, and these are at best educated guesses. However, with proper housekeeping of local bird records, we might eventually be able to search for the answers to these questions. For example, reliable long-term data coupled with environmental modelling showed that the Indian Ocean Dipole event (a phenomena where the Indian Ocean’s western section becomes unusually warmer than the eastern section) led to an influx of Red-necked Phalaropes to the region around Kenya in 2019/2020). Our continued and collective efforts to document Singapore’s birds will surely play a key role in advancing our knowledge in the years to come.

As for now, while our understanding is limited, the patterns suggest one thing: get your gears prepared and be on high alert when Cinereous and Streaked Bulbuls start showing up. These two species seem to serve as messengers for the rendezvous of regional birds rare in Singapore. There are many species on our checklist to look out for: Silver-rumped Spinetail, Whiskered Treeswift, White-bellied Woodpecker, Great Slaty Woodpecker, Malayan Black Magpie. Or perhaps other megas not even on the Singapore checklist – I’d like to place an order for a Brown-backed Flowerpecker please!

We recently contributed an article to BirdingASIA to highlight these avifaunal records from our community during the 2020-2021 season and the possible implications behind them. As the national borders start opening up, many of you who picked up this obsession hobby of birding recently must be craving to, or might have already started to explore beyond Singapore. If you’re keen to read more about birding news from the Asian region, do consider subscribing to the Oriental Bird Club! You’ll receive two copies of BirdingASIA with more exciting articles from the region, as well as one copy of the Journal of Asian Ornithology where latest research on regional avifauna are highlighted. (Just for the record, the Singapore Birds Project is not affiliated in any way to the Oriental Bird Club. We do not get any commission or benefits from promoting them.).

Happy birding, and please do share your sightings if you happen to come across any of these rarities and submit your records to the Singapore Bird Database for proper archival!

Table of records of locally significant Sundaic species, as displayed in the chart above (2014-2021)

Species Date Location Count
Yellow-vented Flowerpecker Dicaeum chrysorrheum 27 Jul 2014 (imprecise) River Safari 1
Yellow-eared Spiderhunter Arachnothera chrysogenys 20 Nov 2014 to 22 Nov 2014 CCNR 1
Thick-billed Flowerpecker Dicaeum agile 22 Nov 2014 Central Catchment Nature Reserve 1
Yellow-vented Flowerpecker Dicaeum chrysorrheum 22 Nov 2014 CCNR 1
Green Broadbill Calyptomena viridis 27 Nov 2014 to 29 Nov 2014 East Coast Park 1
Green Broadbill Calyptomena viridis 25 Dec 2014 Pulau Ubin 1
Black-winged Flycatcher-shrike Hemipus hirundinaceus 28 Jun 2015 Pulau Ubin 1
Yellow-vented Flowerpecker Dicaeum chrysorrheum 26 Sep 2015 Dairy Farm Nature Park 1
Yellow-vented Flowerpecker Dicaeum chrysorrheum 14 Feb 2016 Bukit Timah Nature Reserve 1
Little Green Pigeon Treron olax 16 Mar 2016 Jelutong Tower 1
Yellow-vented Flowerpecker Dicaeum chrysorrheum 09 Jul 2016 Lower Peirce Reservoir 1
Black-and-red Broadbill Cymbirhynchus macrorhynchos 24 Aug 2017 Pulau Ubin 1
Black-winged Flycatcher-shrike Hemipus hirundinaceus 20 Jan 2018 CCNR 1
Great Slaty Woodpecker Mulleripicus pulverulentus 02 May 2018 to 12 May 2018 Bukit Timah Nature Reserve 1
Black-winged Flycatcher-shrike Hemipus hirundinaceus 06 May 2018 Pulau Ubin 1
Black-winged Flycatcher-shrike Hemipus hirundinaceus 24 Sep 2018 Pulau Ubin 1
Little Green Pigeon Treron olax 12 Oct 2018 Windsor Nature Park 1
Black-winged Flycatcher-shrike Hemipus hirundinaceus 21 Oct 2018 Pulau Ubin 1
Large Woodshrike Tephrodornis virgatus 22 Oct 2018 Jelutong Tower 1
Yellow-vented Flowerpecker Dicaeum chrysorrheum 05 Jan 2019 to 21 Jan 2019 Bukit Timah Nature Reserve 2
Black-and-red Broadbill Cymbirhynchus macrorhynchos 20 Mar 2019 Sungei Buloh Wetland Reserve 1
Black-winged Flycatcher-shrike Hemipus hirundinaceus 22 Apr 2019 Dairy Farm Nature Park 1
Black-winged Flycatcher-shrike Hemipus hirundinaceus 22 Jun 2019 Pulau Ubin 1
Black-and-red Broadbill Cymbirhynchus macrorhynchos 07 Jul 2019 Pulau Ubin 1
Black-winged Flycatcher-shrike Hemipus hirundinaceus 14 Jul 2019 to 21 Jul 2019 Pulau Ubin 1
Black-naped Monarch Hypothymis azurea 07 Sep 2019 to 18 Sep 2019 Pulau Ubin 1
Black-naped Monarch Hypothymis azurea 18 Oct 2019 to 24 Oct 2019 Singapore Botanic Gardens 1
Yellow-vented Flowerpecker Dicaeum chrysorrheum 29 Oct 2019 Bukit Timah Nature Reserve 1
Yellow-vented Flowerpecker Dicaeum chrysorrheum 16 Nov 2019 Bukit Timah Nature Reserve 1
Thick-billed Flowerpecker Dicaeum agile 16 Dec 2019 to 25 Dec 2019 Dairy Farm Nature Park 3
White-bellied Erpornis Erpornis zantholeuca 16 Jun 2020 to 17 Jun 2020 Bukit Timah Nature Reserve 1
Black-naped Monarch Hypothymis azurea 25 Jan 2021 Pulau Ubin 1
Black-thighed Falconet Microhierax fringillarius 12 Feb 2021 Yishun Street 21 1
Scarlet Minivet Pericrocotus speciosus 25 Feb 2021 Goldhill 1
Black-naped Monarch Hypothymis azurea 15 Mar 2021 Jurong Lake Gardens 1
Black-naped Monarch Hypothymis azurea 20 Mar 2021 Clementi Woods Park 1
Green Broadbill Calyptomena viridis 06 Apr 2021 to 22 Aug 2021 Pulau Ubin 1
Black-thighed Falconet Microhierax fringillarius 30 May 2021 Goldhill 1
Malayan Black Magpie Platysmurus leucopterus 09 Jun 2021 Hindhede Quarry 1
Black-winged Flycatcher-shrike Hemipus hirundinaceus 21 Jun 2021 Chek Jawa 1
Black-thighed Falconet Microhierax fringillarius 09 Jul 2021 to 11 Jul 2021 Jalan Mashhor 1
Black-naped Monarch Hypothymis azurea 12 Oct 2021 to 13 Oct 2021 Central Catchment Nature Reserve 1
Yellow-vented Flowerpecker Dicaeum chrysorrheum 26 Oct 2021 to 14 Jan 2022 Bukit Timah Nature Reserve 1
Black-winged Flycatcher-shrike Hemipus hirundinaceus 05 Nov 2021 Pulau Ubin 1
Yellow-vented Flowerpecker Dicaeum chrysorrheum 22 Nov 2021 to 29 Nov 2021 Bukit Timah Nature Reserve 1
Scarlet-breasted Flowerpecker Prionochilus thoracicus 29 Nov 2021 Bukit Timah Nature Reserve 1

References

Nussbaumer, R., Gravey, M., Nussbaumer, A., & Jackson, C. (2021). Investigating the influence of the extreme Indian Ocean Dipole on the 2020 influx of Red-necked Phalaropes Phalaropus lobatus in Kenya. Ostrich92(4), 307-315.

Sin, Y.C.K., Narayanswamy, R., Ng, D., Chia, S., Ng, E., & Kennewell, M. (2022). Beyond the pandemic: gems from Singapore in 2020-2021. BirdingASIA, 37, 101-108.

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